Come April 2015, the Hubble Space Telescope (HST) will mark its 25th anniversary observing the cosmos. Launched in April 1990 aboard the space shuttle Discovery, the HST was built primarily by the US Space Agency, NASA, with contributions from the European Space Agency, ESA. The motivation behind building a space-based telescope as opposed to a ground-based telescope was the absence of atmospheric distortions and light pollution, to which ground-based telescopes are susceptible. Hubble makes observations in the visible electromagnetic spectrum (VIBGYOR) and also in the infrared (IR) and ultraviolet (UV), which flank the visible wavelengths. This entry follows the journey of the Hubble and the plethora of science it has given us (rest assured, pretty pictures included).
Although Hubble has given us an unprecedented view of some of the earliest galaxies in the universe, its early years of operation were rather... shaky. Let us go back to the first few weeks after the launch of Hubble. Being a rather expensive project, there was excitement within the scientific community about the first images that the Hubble would send back to Earth. An example is shown below:
Although the Hubble images were considerably better than the ground-based observatories of the time, they were still nowhere near as sharp as scientists had expected them to be. The telescope wasn't focusing properly. After analysing the images, it was understood that the primary mirror on Hubble was not of the correct shape. Understandably, Hubble became the butt of many jokes. While possible solutions to this problem were being explored, the telescope continued to observe simpler science targets and scientists developed ways to enhance images using image processing techniques.
In December 1993, the first service mission was launched aboard the space shuttle Endeavour. This mission installed the optical corrections necessary in addition to upgrading one of the primary cameras to the improved Wide Field and Planetary Camera 2 (WFPC2). This resulted in a dramatic increase in picture quality and NASA deemed the Hubble Space Telescope a success. Shown below is the improvement in imaging:
Although Hubble has given us an unprecedented view of some of the earliest galaxies in the universe, its early years of operation were rather... shaky. Let us go back to the first few weeks after the launch of Hubble. Being a rather expensive project, there was excitement within the scientific community about the first images that the Hubble would send back to Earth. An example is shown below:
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| Left: Images from ground based observatories of the time. Right: One of the first images from the HST. |
In December 1993, the first service mission was launched aboard the space shuttle Endeavour. This mission installed the optical corrections necessary in addition to upgrading one of the primary cameras to the improved Wide Field and Planetary Camera 2 (WFPC2). This resulted in a dramatic increase in picture quality and NASA deemed the Hubble Space Telescope a success. Shown below is the improvement in imaging:
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| Left: Uncorrected image of galaxy Messier 100 (M100). Right: M100 imaged using the new and improved WFPC2 camera. |
The pretty pictures were just beginning to flow! Here are a few examples of some of the most iconic Hubble pictures:
1. The Eagle Nebula
One of the most famous Hubble images, the Eagle Nebula, also known as the 'Pillars of Creation', is a stellar nursery. The gas and dust regions are actively giving birth to new stars.
2. Mars
Hubble image of our neighbouring red planet.
3. ESO 510-G13
A spiral galaxy like our own Milky Way. The visibly warped spiral arms may have resulted due to its interaction with a neighbouring galaxy.
4. Messier 9 Globular Cluster
A globular cluster is a densely packed collection of stars. Messier 9 (M9) is very close to the centre of our galaxy. Its total luminosity is around 120,000 times that of the Sun.
5. Hubble Ultra Deep Field
The iconic Ultra Deep Field image, this contains some of the earliest galaxies, up to 13 billion years old (the age of our universe is 13.8 billion years). Taken in 2004, this image contains approximately 10,000 galaxies.
6. Abell 2218 Galaxy Cluster
A galaxy cluster is a very massive collection of galaxies that are bound together by gravity. The immense gravity of a cluster is strong enough to stretch and shear light, which gives rise to the strikingly beautiful arcs around the centre of the cluster. This phenomenon is known as gravitational lensing.
The Hubble has undoubtedly been one of the most vital tools for advancing astronomy. It has expanded our knowledge of the cosmos beyond imagination. From estimating the age of the universe using very distant supernovae (see earlier posts!) and discovering that almost all massive galaxies have supermassive black holes in their centre, to detecting previously unknown comets and imaging proto-planetary that lead to formation of extra-solar planets, the science that Hubble has provided is staggering!
Hubble received its final service mission in 2009 to prolong the functioning of its instruments, before it will be succeeded by the James Webb Space Telescope (JWST) in 2018/19. The harsh reality is that Hubble's instruments will eventually stop functioning and it will be defunct, but that will not take away one bit the impact it has had on our understanding of the universe at every imaginable scale. All good things must come to an end, but the Hubble is just turning 25 years young!
All images courtesy Hubble picture gallery. More pictures can be found here! http://hubblesite.org/gallery/
